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US-12617041-B2 - Method and apparatus for filamentation of workpieces not having a plan-parallel shape, and workpiece produced by filamentation

US12617041B2US 12617041 B2US12617041 B2US 12617041B2US-12617041-B2

Abstract

A method for filamentation of a dielectric workpiece has a workpiece with a thickness between 0.5 and 20 mm is provided. The workpiece has boundary surfaces delimiting the workpiece. The thickness of the workpiece varies spatially and/or at least one of the boundary surfaces delimiting the workpiece has at least one curvature with a radius of curvature between 0.1 μm and 10 m. The dielectric workpiece can have a specially formed edge.

Inventors

  • Andreas Ortner
  • Fabian Wagner
  • Albrecht Seidl
  • Frank-Thomas Lentes

Assignees

  • SCHOTT AG

Dates

Publication Date
20260505
Application Date
20210917
Priority Date
20151005

Claims (19)

  1. 1 . A dielectric workpiece comprising: a plurality of boundary surfaces delimiting the workpiece; the workpiece has a thickness between 0.5 and 20 mm, wherein the thickness varies spatially and/or at least one of the boundary surfaces has at least one curvature with a radius of curvature between 0.1 μm and 10 m, the workpiece has an edge having a roughness RMS from 1 to 5 μm determined by a roughness measurement using an atomic force microscope and/or a white light interferometer, wherein the edge has a material with a material property that differs from a remaining portion of the workpiece, wherein the edge is formed by determining a vector standing orthogonally on a local surface that is the mathematical surface normal vector so that a filament of the dielectric workpiece is aligned at an angle that is represented by the surface normal vector, wherein the filament is formed of a cavity, wherein the filament is a plurality of filaments that are produced in different height sections of the workpiece, and wherein one of the plurality of filaments has a starting point that is also an end point of another produced filament of the plurality of filaments, and wherein the starting point of the one of the plurality of filaments is identified by a scattering center in the workpiece.
  2. 2 . The dielectric workpiece of claim 1 , wherein the material property is selected from the group consisting of phase content, refractive index, density, and any combinations thereof.
  3. 3 . The dielectric workpiece of claim 1 , wherein the workpiece is glass.
  4. 4 . The dielectric workpiece of claim 3 , wherein the glass is an aluminosilicate or borosilicate glass.
  5. 5 . The dielectric workpiece of claim 1 , wherein the workpiece has a wedge-like shape.
  6. 6 . The dielectric workpiece of claim 1 , wherein the workpiece is an ampoule or a tube.
  7. 7 . The dielectric workpiece of claim 1 , wherein the workpiece is a curved or warped sheet or exhibits waviness.
  8. 8 . The dielectric workpiece of claim 1 , wherein the plurality of boundary surfaces are two delimiting surfaces that are not formed parallel to each other.
  9. 9 . The dielectric workpiece of claim 8 , wherein the workpiece has an irregular gradient.
  10. 10 . The dielectric workpiece of claim 1 , wherein the thickness of the workpiece that is delimited by the boundary surfaces that are not plane-parallel to each other and vary along an extension of the workpiece.
  11. 11 . The dielectric workpiece of claim 1 , wherein at least one of the plurality of boundary surfaces exhibit curvature.
  12. 12 . The dielectric workpiece of claim 1 , wherein the workpiece is formed so that a lateral extension of the boundary surfaces delimiting it is greater by at least one order of magnitude than its thickness.
  13. 13 . The dielectric workpiece of claim 1 , wherein the workpiece is in the form of a slice in which a structure has been introduced on a surface of the boundary surfaces in order to optimize reflection properties of the workpiece that is a pyramidal structure.
  14. 14 . The dielectric workpiece of claim 1 , wherein the workpiece is a rectangle with edges that have finite radii in the millimeter range.
  15. 15 . The dielectric workpiece of claim 1 , wherein the workpiece has an angular shape with rounded edges.
  16. 16 . The dielectric workpiece of claim 1 , wherein the material property is phase content.
  17. 17 . The dielectric workpiece of claim 1 , wherein the material property is refractive index.
  18. 18 . The dielectric workpiece of claim 1 , wherein the material property is density.
  19. 19 . The dielectric workpiece of claim 1 , wherein the filament is formed of a tubular cavity.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a divisional of prior application Ser. No. 15/945,992, filed Apr. 5, 2018 that is a continuation of International Application No. PCT/EP2016/073692 filed on Oct. 4, 2016, which claims benefit under 35 U.S.C. 119(a) of German Patent Application No. 10 2015 116 846.4 filed Oct. 5, 2015, the entire contents of which are incorporated herein by reference. BACKGROUND 1. Field of the Invention The invention relates to a method for filamentation, in particular for cutting a dielectric workpiece which has a shape deviating from a predefined nominal contour, and also relates to a dielectric workpiece having a specially formed edge. Methods for separating dielectric workpieces, e.g. wafers, by subjecting them to laser radiation have been state of the art for many years. In recent years, the technique of filamentation has developed in which a workpiece is subjected to a laser which has a wavelength in the transparency range of the workpiece to be separated. The impact of the laser occurs in the form of pulsed ultrashort laser radiation, and the pulse may be in the form of an individual pulse or in a so-called burst mode, i.e. in the form of discrete packets. In this way, so-called filaments can be produced in dielectric workpieces such as glass, for example. A filament is known to be an elongated formation in the workpiece with a modified nature of the workpiece in the area of this formation. For example, microcracks and/or structural changes are caused in the area of the filament, e.g. in the form of crystallization or formation of new phases. The so formed defects in the workpiece are arranged along a predefined damage line and thus are effective as starting points for later separation of the workpiece along this line. Such a method is described in DE 10 2012 110 971 A1 by way of example. Furthermore, international patent application WO 2014/111385 A1 discloses a method and a device for laser-based processing of sheet-like substrates. In this case, a substrate, e.g. a wafer or a glass element, is separated along a plurality of cutting lines, by producing a line focus in the workpiece so that induced absorption occurs, which induces crack formation in the substrate material. Here, the filament is in the form of a continuous formation from the starting point of filament formation to at least one surface of the workpiece, i.e. it is uninterrupted. Furthermore, EP 2 781 296 A1 describes a two-step process in which filaments, i.e. damage zones, are first induced along a predefined course line, and in a further step a material removal and/or deformation step is performed, for example using a CO2 laser, so that the workpiece can be separated along the course line. International patent application WO 2012/006736 A2 describes a method for processing a transparent substrate for preparing a separation step. Here, filaments are produced inside the substrate by means of a laser, and it is also possible to form trench-like indentations in at least one surface of the substrate. Depending on the exact setting of the laser parameters, the filaments are formed inside the substrate due to self-focusing of the laser beam, and it is also possible to form a plurality of filaments in the substrate in a row. In a further step, the substrate is separated along the so produced defect line. However, the methods mentioned above reach their limits when workpieces are to be separated that do not have a plane or flat shape, e.g. the shape of a slice or sheet or of a ribbon which is delimited by plane-parallel surfaces subject to manufacturing tolerances within a typical range. For example, the problem of warped sheets, such as glass sheets, has been known for a long time. Moreover, such sheets often exhibit a certain waviness or, more generally, a thickness variation along their extension, so that they generally deviate from a flat shape. Since the positioning of the filaments relative to the surfaces is decisive for a good reproducibility of the induced damages in order to provide for separation with a minimum of errors and rejects, an increased number of rejects is caused with workpieces that are not optimally shaped. Furthermore, with the previously known methods it is not possible at all to achieve filamentation and separation of workpieces that have a shape deviating more strongly from the flat, planar shape or which have a particularly large thickness. SUMMARY There is thus a need for a method for filamenting and separating workpieces that have a shape deviating from the flat shape, e.g. a wedge-like shape, and/or a large thickness, or distinguished by boundary surfaces having curvatures, for example. An object of the invention is to provide a method which permits to separate a workpiece having a large thickness and a shape deviating from the flat shape, and to provide a workpiece produced in this way, in particular with an edge formed according to this method. The method according